The present invention relates to a plasma processing apparatus for processing a wafer disposed within a processing chamber inside a vacuum vessel with a plasma generated within the processing chamber and to a sample stage disposed in this plasma processing apparatus. More particularly, the invention relates to a plasma processing apparatus operative to perform processing while adjusting the temperature of a sample stage which is disposed in such a processing chamber and on which a wafer is mounted. The invention also relates to this sample stage.
In the above-described plasma processing apparatus, it has been heretofore considered to process vertically adjacent films (so-called multilayer film) formed on the surface of a sample such as a substrate (e.g., a semiconductor wafer) within the same processing chamber in such a way that the wafer is not taken out of the processing chamber during the processing of each film, in order to etch the multilayer film in a shortened time. This apparatus is required to perform finer processing at higher accuracy. To realize this, it is necessary that the uniformity of the wafer profile obtained as a result of etching of films to be processed be enhanced along its plane (i.e., radially and circumferentially). For this purpose, the temperature of a sample stage having a top surface on which a wafer is mounted and thus the temperature of the wafer have been adjusted to values appropriate for the processing during the processing of the films.
A known technique of adjusting such temperatures is disclosed, for example, in JP-A-2002-231421. That is, the top portion of a sample mounting stage constituting a surface on which a wafer is mounted is made of a disk-like member made of a ceramic. A heater is connected to this sample mounting stage and disposed below this stage. The temperature of the ceramic disk and the temperature of the wafer mounted on top of the disk are made appropriate for processing by adjusting the amount of heat generated by the heater. Especially, JP-A-2002-231421 discloses a ceramic heater consisting of a ceramic substrate in a disk-like form and a resistive heating element formed on or in the substrate. Another resistive heating element consisting of at least two circuits split circumferentially is formed in an outer peripheral portion of the ceramic substrate. A further resistive heating element made of a separate circuit is formed inside the resistive heating element disposed in the outer peripheral portion.
In this conventional technique, the heaters, i.e., the resistive heating elements, are made of a material prepared by mixing an electrically conductive material or semiconductor material into a metal or a heatproof resin. Connectors are placed in through-holes formed in the sample stage, and serve to supply electric power. Heaters are disposed in two different areas of the sample stage which are located around the center and in an outer peripheral portion, respectively. The heaters are connected with power supplies via their respective connectors such that different levels of electric power may be supplied to the heaters.
In the above-described conventional technique, the aforementioned configuration makes it possible to obtain a distribution of temperature values varying from the center of the wafer toward the outside (i.e., in the radial direction of the wafer in a disk-like form) by controlling the temperature of the central portion and the temperature of the outer peripheral portion of the sample stage and of the wafer mounted on top of it to their respective desired values.